1. Field of Invention
This invention relates generally to transillumination techniques for examining the morphology of human organs, and more particularly to a diaphanoscopic system adapted to carry out breast examinations and constituted by a portable light-beam projector of controllable intensity and limited duration operating in conjunction with a camera assembly to produce chromatic diaphanographs useful for diagnosis.
2. Prior Art
An elementary and well-known form of transillumination is candling in which an egg or other relatively translucent article is examined by being held between a light source and the eye of the observer. Portions of the human anatomy are more or less permeable to light rays, and it is known that by detecting the amount of light passing through an anatomical region of interest, a physician or trained observer can learn about the morphology thereof.
In its medical applications, transillumination or diaphanoscopic examination is presently employed in studying sinus cavities, the scrotum and fluid cavities in the head. Transillumination is of particular value in detecting and diagnosing the onset of hydrocephalus, which involves an abnormal increase in the amount of cerebrospinal fluid within the cranial cavity. This condition, which is not uncommon in premature infants, is characterized by the expansion of the cerebral ventricles accompanied in some instances by enlargement of the skull and the resultant atrophy of the brain. Because there is a distinct possibility that mental retardation will result from hydrocephalus, early detection of this condition is desirable so that appropriate corrective measures can be taken.
The Johnson U.S. Pat. No. 3,674,008 and the Thomas U.S. Pat. No. 3,527,932 describe the clinical procedure for diagnosing hydrocephalus by transillumination. In this technique, a flashlight is placed against the infant's skull, the remainder of the skull being examined by the physician for light transmission. For a normal skull with the fluid within the cranial cavity at a normal level, the skull will be relatively opaque and little light will pass therethrough. If, however, there is a large quantity of fluid in the immediate vicinity of the light source, the skull will then be fairly translucent so that the light can be seen by the observer. Other prior art patents of interest which relate to transillumination are the Schwartz U.S. Pat. No. 2,161,688 and the Goldman U.S. Pat. No. 3,769,963.
While it will be recognized that a system in accordance with the present invention has many other medical applications for morphological diagnosis, the primary concern of the present invention is with transillumination for breast examination, particularly in connection with the diagnosis of mammary carcinoma; for the incidence of such cancer appears to be on the rise, at least in the United States, and early detection thereof is highly desirable. Because the most commonly used technique for breast examination is radiology, and there is a growing public alarm with adverse effects that may result from exposure to X-rays, the need now exists for a diagnostic procedure that is simple, effective and yet altogether innocuous.
The three most widely used clinical techniques for mammary examination are thermography, radiology and ultrasonography. Thermography, which detects infra-red emission from the internal structure of the region under examination, is now frequently employed in the diagnosis of mammary carcinoma, for it is an inexpensive procedure and perfectly safe. Thermography reveals functional and metabolic alterations, the presence of a malignant tumor being detected by reason of its thermogenic power.
However, the margin of error with thermography is fairly high because of so-called false positives and negatives. An internal nodule which emits a relatively large amount of infra-red energy is generally identified as a carcinoma and may be identified as such by thermographic examination. But the nodule having such thermal properties may in fact not be a carcinoma, as evidenced by X-ray or other techniques, and therefore in thermography represents "a false positive." On the other hand, a nodule which exhibits a low level of thermogenic power may be dismissed by thermographic examination and yet prove to be a "cold" carcinoma, this being characterized as "a false negative."
Apart from the hazards of radiation exposure which are an inevitable concomitant of radiological examination, the record produced thereby has distinct limitations, for it is constituted by a black and white shadowgraph whose pattern is determined by the relative permeability of internal structure to X-rays. Thus fatty tissue is effectively transparent to X-rays, whereas a malignant tumor is relatively opaque, while other physiological elements are more or less opaque. Hence the resultant shadowgraph reveals the irradiated internal structure in terms of gray scale graduations whose proper interpretation requires a high order of skill and experience on the part of the radiologist.
Ultra-sonography, which explores internal structure by means of a scanning beam of ultrasonic energy in a pulse echo technique, depends on the degree to which structural elements in the path of the beam absorb or reflect this energy. Ultra-sonography also has inherent limitations, for certain internal elements may differ physiologically or pathologically and yet possess virtually the same properties with respect to the ultrasonic beam. Hence differences which may be significant medically are not made evident by this technique.
Though transillumination for the detection of hydrocephalus is a widely used technique, in the field of mammary examination its clinical applications have heretofore been much more limited because of certain practical considerations which will later be analyzed. The medical literature in this field is, therefore, relatively scanty. Among the few published articles is that by Gros et al. in J. Radio. Electrol. 53, 297-1972, "Diaphanologie Mammarie."
Yet, as pointed out recently by DiMaggio et al. of the Institute of Radiology of Padua University of Italy in the June 1978 issue of Senologia (page 69 et seq.) in an article entitled "Diaphanoscopic Study of Dystrophic Alterations of the Breast," the transillumination technique is highly useful in mammary examination, particularly if used to complement better known techniques such as radiological observation; for what may fail to show up in one technique may in many instances be made evident by the other.
The authors of this article report the results obtained from the diaphanoscopic mammary examination of several thousand women. The conclusion reached is that this technique makes it possible to find lesions in fibrous mamma, to discover the presence of papillomas, even where there is no secretion of the manilla, and to locate opaque nodules which are "suspect." Moreover, with transillumination, one can, according to this article, obtain a correct reading of the cystic nature of hypertransparent nodules as well as a correct reading of sclerocystic regions. Also, it becomes possible in cases of normotransparent dystrophic areas, to remove the suspicion of cancer as to these areas.
Hence with transillumination, even if one does not exclusively rely on this technique in breast examination, it nevertheless constitutes a valuable adjunct in resolving ambiguities and reducing errors arising in radiological thermographic or other techniques with which the medical profession is presently more conversant.
As distinguished from the radiological technique which merely produces a gray scale shadow of irradiated internal structure, mammary transillumination affords information regarding the observed internal structure in terms of color. When a beam of light is projected through a mammary protuberance and the placement of the beam is such as to pass through fatty tissue, its appearance to the eye of the observer is reddish-orange, whereas vascularization is presented as black striae.
The presence of fibro-glandular tissue which is developed during pregnancy and breast feeding is made apparent by its high degree of opacity. The appearance of cysts in diaphanoscopic examination depends on their content. Thus cysts with a clear content have the same color as their background if they are surrounded by fatty tissue, but they are visible as areas with a somewhat higher transparency if surrounded by less transparent areas because of an intense fibro-glandular proliferation. Cysts with a brownish, cloudy or blue content are distinguishable in terms of color and relative opacity from those with a hematic content.
Thus in transillumination of the breast, the distinguishing features of the internal structure are expressed both chromatically and in terms of relative opacity to light, thereby affording more detailed data than is obtainable with prior techniques.
To take full advantage of transillumination, the requirements which are imposed on the light source are somewhat contradictory. Thus the white light beam must be sufficiently intense and concentrated to permit breast analysis, even with breasts which are highly light-absorbent. On the other hand, the beam must not be so intense as to result in uncomfortable overheating of the breast, with possibly damaging effects.
Moreover, it is not sufficient that the light intensity be such as to render the internal structure visible to an examinining physician, for it must be adequate to permit the taking of photographs. It must be borne in mind that photographic film responds photochemically to light and has a more marked response to so-called actinic rays. Actinic rays refer to that portion of the light spectrum that is rich in green, blue, violet and ultraviolet rays.
Inasmuch as a breast under transillumination is predominantly reddish-orange in coloration, even when irradiated by an intense white light it produces a somewhat dim image in colors with respect to which photographic film has a relatively poor response. These factors create difficulties in the taking of color photographs, particularly of the "instant" film type.
In taking a color photograph of a transilluminated breast, this must be done in a darkened room so that ambient light does not interfere with the low-level light emitted from the breast and the only light incident to the camera lens are rays arising from the breast. And the picture cannot have an unduly long time exposure, for the examining physician who is manipulating the light beam with respect to the breast protuberance must be in a position to snap a picture as soon as he observes internal structure of interest. Thus a flashlight-produced beam, which is adequate in skull examination, is totally unsuitable for breast examination.
Another factor that must be taken into account is the danger of electrical shock. To generate a light-beam of adequate intensity, use must be made of a high wattage lamp powered from the standard a-c line rather than by low voltage batteries. For breast examination, the light-beam source must be portable in nature so that it can be manipulated and oriented with reference to the breast. Since the lamp necessarily has a power cable leading thereto, this could be hazardous both to the doctor and the patient if the cable carries a high voltage and the lamp housing is of electrically-conductive material. This may be necessary to dissipate the heat generated by the high-wattage lamp; for with an incandescent lamp, a substantial portion of the applied electrical energy is converted into heat.
Still another factor which comes into play in breast examination is the facility in which the examination is conducted. Where the facility is a well-staffed clinic with doctors, nurses and other attendants, then it is possible for, say, one nurse to manipulate a light-beam source with respect to the breast under the direction of the examining physician, while another nurse or paramedical assistant operates a camera and by means of a range finder, focuses onto the breast under examination and takes a picture when instructed to do so by the physician.
But the profession of medicine, at least in the United States and in many European countries, is largely a private practice. The typical patient who is concerned about the condition of her breasts will therefore consult a doctor in his office. This doctor usually has no more than one assistant and has little time to spare in setting up for a breast examination. Ideally, the nature of the transillumination equipment available to the doctor should be such that he is able to carry out an examination and take photographs in a matter of minutes without an elaborate procedure requiring trained assistants. However, existing transillumination equipment for this purpose falls far short of this ideal.